Photodetectors are used in various applications including communications, imaging and power generation. When a photodetector is exposed to light within an operating range of wavelengths, electron-hole pairs are generated due to light absorption by certain materials of the photodetector. These generated electron-hole pairs are transported to form a photocurrent under an applied electric bias. In some super-lattice based photodetectors for operating wavelengths in the range 3-30 μm, the hole mobility is relatively low. This can inhibit the performance of the photodetector, particularly at the long-wavelength end of its operating range.